The field of data communication has grown with the pace of new data-routing equipment, switches, and techniques that have enabled all types of data to be transmitted over wide area networks (WAN) faster and more reliably. Manufacturers are competing to introduce faster data routers and better methods for synchronizing and integrating state-of-the-art equipment provided by a variety of competitors.
Integrating various types of proprietary data routing equipment for network communication involves, among other things, dealing with different rates of data processing and transfer in terms of interfaces and interfacing data network protocols between disparate data networks.
One of the more recent advances in data routing over large WANs such as the well-known Internet network, for example, is the implementation of synchronized optical network or SONET protocol and equipment. SONET is a standardized protocol implemented along with specialized network equipment to create a special network that allows multiple data lines transmitting data at different rates and formats to be multiplexed over a single optical carrier typically at a higher speed through a SONET portion or section of the network.
A simplified example of SONET might involve multiplexing, for example, a T1 line transferring data at 1.54 Mbits/s, a T3 line transferring data at 44.736 Mbits/s, and a E1 line transferring data at 2.048 Mbits/sec, onto a single fiber-optic cable after processing the separate streams through a SONET Multiplexor system. The result is a single combined stream transferred at a higher rate, typically 51.48 Mbits/s associated with fiber-optics technology. At the other end of the SONET fiber-optic cable, the data streams are de-multiplexed and resume their original formats, characteristics and transfer rates. SONET is a midstream solution for getting data across the network between oftentimes disparate vendor interfaces. Data may travel in this fashion through established SONET network paths until the streams are terminated as far as SONET format is concerned and converted back to user formats.
Much detailed information on the SONET structure and parameters is publicly available, therefore the publicly-available detail will not be provided here except to say that the application of SONET enables subscribers to configure their router interfaces so that a multiple of such interfaces on a single router become dedicated SONET lines.
Another convention in the art of data transfer and switching is termed automatic protection switching (APS). APS comprises a protocol and software that enables a plurality, typically an aggregated group, of primary lines egressing from a router to be individually backed-up by a single backup line dedicated for the purpose.
In one application, APS is used to provide some redundancy for a group of dedicated SONET line interfaces of a router. For example, a group of separate router interfaces on the egress side of the router that are connected to SONET equipment is backed-up by a dedicated interface (backup line). Typically, for APS switchover from a primary terminal to a backup to be successful, it must occur within 50 milliseconds (ms), which is a standard set within the protocol. Also, of course, all of the primary terminal parameters, such as data transport protocols and state information must be identically implemented at the backup terminal to obtain a successful handshake at the other end of the communication path. APS fault protection is transparent to the other communicating party or system. Moreover, in the case of more than one primary SONET line requiring or requesting backup at a same time, a priority scheme may be implemented to enable priority selection of a line for backup or “relocation” as it is termed in the art.
A data router known to the inventor uses a distributive processing architecture to process data. The router is termed a terabit network router (TNR) developed to improve data routing efficiency in general, and to enable users to scale router capacity easily. The distributed processing components include line cards that interface between the internal router domain and the external connected network, fabric cards and interconnections that comprise an internal data packet routing network within the router itself, and control cards that provide control routines, messaging, and in some cases special packet processing duties.
Each card in a TNR typically has a dedicated, on-board processor and memory. Each card also typically has a plurality of physical interfaces comprising ingress/egress ports for transferring data. The present invention in preferred embodiments primarily focuses on the use of SONET APS protection on a distributed processor router, and focuses more particularly on a novel implementation and use of APS software in a distributed processor system.
Prior art routers employing one, or at most a few processors, can use conventional APS software because all of the processing involved happens on one processor for all of the SONET lines, and there is a designated backup, as will be described further below with reference to a prior-art example of FIG. 1. It was described above that the standard of 50 ms for switchover must be adhered to for APS to be successful. If a switchover process times out before completion, the communication path involved will not exhibit a successful handshake and transmission will fail. A distributed processor system cannot perform a switchover within the required time period using standard APS software. Therefore, what is clearly needed is a method and apparatus (software) that will allow APS to be successfully practiced on a multi-processor router.